The system of connecting conduits made of a flexible material using a locking ring which may be moved backwards and forwards in an axial direction over the push-in sleeve is already widely known. If the locking ring is pushed into its operative position, the collet chuck components press against the conduit walls and grip them firmly. Where the connecting operation involves conduits made of a flexible material, the flexible material is squeezed inwards to a greater or lesser degree by the collet chuck components. This increases the firmness of the grip on the conduit since on the one hand the conduit material which is under elastic compression exerts an outward radial force on the collet chuck components and these in turn are held by an elastic force against the locking ring. On the other hand, compression or nipping of the conduit material, even if it is very slight, creates a positive axial lock. In the case of conduits made of a rigid material, that is primarily with metal pipes, these effects do not occur. In order to obtain an equally firm hold on the conduit, it will be necessary to clamp the collet chuck components harder against the conduit. Failing this, the end of the conduit might work free from the adaptor connecting piece, for example in the event of a high pressure build up or load fluctuations inside the conduit. Increased collet chuck components clamping pressure means that it will be necessary to exert a correspondingly greater force to displace the locking ring in an axial direction. This increases operating difficulties considerably. There is also a danger that the locking ring, which has an axial displacement facility, may be moved backwards unintentionally into its inoperative position, thereby releasing the connection.
The object of this particular invention was therefore to produce an adaptor connecting piece of the type mentioned at the outset which would produce a firm hold on the end of the conduit inserted not only in the case of flexible materials but also for metal conduits, even where the conduit is subjected to high pressure factors or regularly fluctuating load levels, where the force needed to form the connection is relatively small and may be exerted manually.
The present invention solves this problem by presenting a system which is of particular significance to connections involving the use of metal conduits and in which the locking ring is linked, in its operative position at least, with the collet chuck components by means of a self-locking screw connection, the said locking ring being equipped with an internal thread and the push-in sleeve being equipped with a corresponding external thread in the section containing the collet chuck components, such that the collet chuck components with their thread section are projected conically outwards with the locking ring in its inoperative position and that around the internal circumference of the push-in sleeve at a point opposite the external thread at least one ring tooth protrudes inwards over all the collet chuck components.
The locking ring is thus screwed onto the collet chuck components during assembly; the resultant amount of force required to operate the unit is relatively small, since the axial movement of the screw action forcing the collet chuck components inwards is very low. The angle of incline along the self-locking section is kept small enough to ensure that the locking ring cannot be released unintentionally. In addition, the ring tooth which is fitted to the unit concentrates effective forces at the tooth.
The adaptor connecting piece specified here is suitable not only for use with metal conduits, but is also ideal for conduits made of a flexible material, ensuring a firm hold on the conduit inserted at all times. The unit is also easy to operate.